The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
A female coupling member and a male coupling member which are detachably connected to each other are usually configured to be connected together by engaging a locking element of the female coupling member into a locking element engagement groove of the male coupling member. The locking element is radially displaceably held in a through-hole gradually reduced in diameter toward the inner side which is formed in a cylindrical body of the male coupling member. When locking the male coupling member, the locking element projects inward from the inner peripheral surface of the cylindrical body to engage in the locking element engagement groove of the male coupling member. According to Japanese Patent Application Publication No. 2008-196603 (JP '603), when in the engaged state, the locking element is held by a sleeve from the outer side.
The female coupling member and the male coupling member are sealingly engaged with each other by a seal member, e.g. an O-ring, to prevent a fluid flowing through the inside of the coupling members from leaking to the outside. As shown in JP '603, there is also a pipe coupling wherein each coupling member is provided with a valve mechanism to close a flow path by the valve mechanism when the coupling members are not connected to each other, thereby preventing leakage of the internal fluid.
The above-described pipe couplings are configured to prevent the internal fluid from leaking to the outside by using a seal member or a valve mechanism. There may, however, be a small leakage of internal fluid adhering around the area of sealing when the coupling members are disconnected from each other, for example. When the internal fluid is a high-viscosity liquid or a corrosive liquid such as the electrolyte of a battery, if the leaking liquid adheres to a movable member such as a locking element, the liquid may solidify or corrode the movable element, resulting in the movable element being stuck to become non-displaceable, causing malfunction. If the liquid collects and solidifies in the locking element engagement groove of the male coupling member, it may be impossible to effect appropriate locking by the locking element.